Photoluminescence quenching

Introduction

In this tutorial we will calculate photoluminesence quenching. We will create excitons by simulating irradiation with a short light pulse of our model system. After switching off the light pulse we will measure the light emitted from the radiatively decaying excitons until every exciton in the system is destroyed.

Input files:

The tutorial is done on a parametric model-system, no input files are required.

System setup

Our system consists of a pure layer of a fluorescent material.

Setup and running Lightforge: Commandline and GUI(SimStack) Tutorials

You can perform this calculation by either creating a settings file manually and starting LightForge via command line, or use the SimStack GUI to setup and submit the computation.

  • The commandline tutorial can be found here.
  • The SimStack tutorial can be found here.

Inspecting the results

The runtime output could be inspected in the files output_job_*. Once the calculation is done, three interesting results of the simulation can be found as plots in the experiments folder.

Experiments folder:

Exciton and photon count over time is shown in excitons_photon_transient.png The luminesence over time is plotted in luminescence.png. In a macroscopic model we expect the number of excitons to change according to: Assuming that the luminescence is proportinal to the exciton density, this equation can to be solved for the luminescence: We fit the luminescene directly measured by lightforge to this model to obtain the macroscopic rate constant ktt. We can see the linear tail of the luminesence corresponding to the independent radiative decay of the excitons. From the slope of the tail we can extract a lifetime of 1.1e-8 s, which agrees with the lifetimes of the fluorescent preset used in the simulation. This can be used as a quality check of the simulation. In the beginning of the luminescence plot we see a non linear decay, corresponding to singlet singlet annihilation at the high initial exciton densities.

Statistics of exciton decay processes are shown in exciton_decay_density_average_*.png. Not that "photons" means the absorption of a photon, whereas "radiative" the emission of a photon. A part of the excitons is generated before the tracking of decay events for the plot is started, that is why the sum of the decay processes is larger then the number of absorped photons.

The results of the search are